Shares of TalkMed Group tumbled yesterday after its chief executive officer, Dr Ang Peng Tiam, was suspended for eight months after a failed appeal against a conviction of professional misconduct and a $25,000 fine.

Dr Ang, a prominent oncologist, is synonymous with TalkMed and easily accounts for 40 per cent to 50 per cent of its revenue. TalkMed has a team of just 13 doctors and a whopping $848 million market value.

His appeal failed, and his punishment was raised from a $25,000 fine to a suspension to begin on July 25.

The counter crashed as much as 16 cents, or 21.48 per cent, to 58.5 cents after the news broke, but found support later and ended the day down 10 cents, or 13.42 per cent, at 64.5 cents on 2.38 million shares done.

RHB Research analyst Jarick Seet said the suspension could reduce TalkMed's net profit by 15 per cent to 20 per cent, but he was surprised the shares did not fall more.

TalkMed assured investors in a statement yesterday that Dr Ang's cases would be handed over to his colleagues, such as Dr Khoo Kei Siong, its chief operating officer.

But the risk remains that Dr Ang's colleagues may not be able to command the same level of fees. Some patients could also opt to see another oncologist altogether.

TalkMed added that it remains "operationally sound", and steps have been taken to minimise disruption to patients and to the business.

Although Dr Ang will not be involved in patient care while suspended, he will still lead the group.

The charges against him stemmed from a complaint by the family of a deceased patient whom he treated in 2010.

The Singapore Medical Council's disciplinary tribunal found Dr Ang guilty of making a false representation to the patient, who was suffering from lung cancer, that there was a "70 per cent" chance of responding to treatment. He also failed to offer surgery as an option.

The Court of Three Judges said it stiffened Dr Ang's sentence because of the "multiple aggravating factors in this case", including Dr Ang's eminence and seniority.